I also do not want the four one one idea from MC. T -T' FSA had a pretty good thing going on, a few stages divided into three. FS was too short with four. PH was good with their system, and I do not know about ST's system.
I would personaly like nine dungeons. I have this vision. It is not something like 3 dungeons then the hardness start, it is four four one, not three six. But you can do them in any order. This might be because I have been playing too much Golden Sun, but I think the four elements from MC/FS/FSA...